I'm a big fan of Sierra Nevada beers, especially the ones on tap at their pub here in town. However, I don't think they really qualify as a "micro" brewery per se. At this point, they've become so big they are just shy of a macro brewery...especially since last year they added even more production.
But last year I went to a little place up in McKinleyville, CA called
Six Rivers Brewery. Nice little pub overlooking the coast, and inexpensive but good food. But the best part about that place was their Kona Moon Porter. I had to take a big growler to go it was so good. Their other beers were also very good, including a Chili Pepper Ale I fully expected to dislike. I think what I like about them is that their brewing area is just off the main tap room, and they brew it up in pretty small batches. I think these small batches keep the flavor of the beers variable, and I appreciate the variety.
I used to like it more when Sierra Nevada was smaller, and their Pale Ale would taste just a bit different for each batch they made. Their seasonals are still different year to year, but I miss the smaller brewery. That being said, I'm very impressed with SNs consistency and their commitment to responsible brewing. They've done a lot for the community here and are incredibly environmentally friendly. Last year they brought in hydrogen fuel cell generators and a huge array of solar panels to power the whole brewery. It's pretty cool that even as a large company, they are willing to sacrifice some profit for the good of the environment.